This application relates to a method and apparatus for minimizing concentration fluctuations of the amount of impurities in an industrial air stream being sent to an air treatment system, such as an oxidizer, a recovery condenser, or a biofilter.
In the prior art, many industrial processes result in impurities in an industrial air stream. Air carrying the impurities must typically be sent to an air cleaning system to remove the impurities. One widely utilized type of system is an incinerator or oxidizer.
An example of the types of applications which may result in impurities being directed into the air stream is a paint spray booth wherein impurities are Volatile Organic Compounds (VOC) which escape into the air surrounding the paint spray booth as a result of the spraying process. Air carrying the VOC impurities is typically directed to an oxidizer, such as a regenerative thermal oxidizer, where the impurities are oxidized into water and carbon dioxide.
There are many challenges in the design and operation of such industrial oxidizers. One challenge relates to the load on the system. Typically, the air stream is directed into a combustion chamber, and a burner within the combustion chamber provides heat to oxidize compounds in the air stream. The air stream may pass through a heat exchanger on the way into the combustion chamber.
As the concentration of impurities in the air stream increases, the temperature within the combustion chamber increases accordingly. That is, as more impurities are burned within the combustion chamber, the temperature of the combustion chamber increases. As the temperature within the combustion chamber increases, the amount of fuel that must be sent to the burner to maintain the necessary combustion temperature within the combustion chamber decreases. If the concentration level in the inlet air stream increases to a particularly high level, the total heat in the combustion chamber may be above that necessary to maintain the combustion chamber temperature, even without any input from a burner. A heat rejection mechanism is then typically actuated to prevent heat build-up.
One heat rejection method is to upscale the oxidizer size so that in the event of unusually high concentration, clean air is introduced into the system to dilute the level of concentration in the industrial air stream. This method requires a relatively large oxidizer, which increases the cost of the oxidizer.
On the other hand, when the concentration of impurities in the air is relatively low, then the fuel requirement to the burner increases.
An oxidizer system which processes a fluctuating concentration level must be able to address both extremes. Thus, oxidizers are typically made larger than would otherwise be necessary, and more expensive. In addition, the amount of fuel required to maintain combustion at low concentration levels is also expensive.
Similarly, the design of other air treatment systems including condensers and biofilters is also affected by extreme fluctuations in the inlet concentrations.
For the above reasons, it would be desirable to maintain the level of concentration as close to a constant as is possible.